Typical aircraft turbofan jet engines include a fan that draws and directs a flow of air into a nacelle and into and around an engine core. The nacelle surrounds the engine core and helps promote the laminar flow of air around the core. The flow of air that is directed into the engine core is initially passed through a compressor that increases the air flow pressure, and then through a combustor where the air is mixed with fuel and ignited. The combustion of the fuel and air mixture causes a series of turbine blades at the rear of the engine core to rotate, and to drive the engine's rotor and fan. The high-pressure exhaust gases from the combustion of the fuel and air mixture are thereafter directed through an exhaust nozzle at the rear of the engine.
Bypass flow is air that is directed around the engine core. In turbofan engines, the bypass flow typically provides the main thrust for an aircraft. The bypass flow also can be used to help slow a landed aircraft. Translatable thrust reversers mounted in the nacelle structure selectively reverse the direction of the bypass flow to generate reverse thrust. The thrust reverser is translatable via a guide system directed by an actuation device.
Several turbofan engine parameters are important to optimize design characteristics and performance. One design consideration for optimizing such parameters includes varying the fan nozzle exit area of a high-bypass ration (BPR) engine during operation by translating the engine's variable fan nozzle to optimize engine performance under various flight conditions. By selectively varying the fan nozzle's exit area, an engine's bypass flow characteristics can be adjusted to match a particular flight condition. One way of varying the fan nozzle exit area involves using a translating sleeve to increase or decrease the exit area. Providing a translating sleeve requires a guide system that properly considers surrounding reacting loads (inboard, outboard, and radial) and efficiently manages contact stresses. Also, translating guide systems require a design to minimize seizing of translating components during use.
Accordingly, a need exists for a guide system for a thrust reverser and/or a variable area nozzle assembly for turbofan aircraft engine that is capable of reacting to inboard loads, as well as outboard and radial loads, and effectively managing contact stresses, while minimizing the potential to seize during use.